Quantum Semiconductors and Optoelectronics

Exploiting topological physics to develop novel and robust optical devices: active/passive, classical/quantum

At the University of Maryland (UMD), research in topological photonics in semiconductors explores how engineered semiconductor and photonic‐chip structures can host topologically protected light states—modes of photon propagation that are robust against defects, disorder and sharp bends—by leveraging concepts originally developed in condensed‐matter physics such as the Quantum Hall effect and topological insulators.

Here are the key aspects of this work:

What “topological photonics” means

• The idea is to transfer the concept of topology (global properties insensitive to small local changes) into optical systems: by designing photonic lattices or resonator arrays with specific symmetries and couplings, one can embed “edge states” or boundary modes that are resilient to fabrication imperfection or scattering. DRUM+3Hafezi Group+3Hafezi Group+3
• For example, in a two‐dimensional lattice of coupled silicon ring resonators fabricated in CMOS‐compatible silicon-on-insulator, UMD researchers demonstrated edge states for photons that navigate around defects without being localized. DRUM
• The research from UMD’s Joint Quantum Institute (JQI) / Department of Electrical & Computer Engineering (ECE) group led by Mohammad Hafezi showed the first direct measurement of a topological invariant (the “winding number”) for photonic edge states—an analog to the quantized conductance plateaus in electronic Quantum Hall systems. Electrical and Computer Engineering+2DRUM+2

Why semiconductors and photonic chips

• By using semiconductor materials (e.g., silicon, silicon nitride, GaAs) and microfabricated photonic circuits, the group combines photonic device design with chip‐scale integration, which enables compact, scalable, and potentially manufacturable platforms for topological photonics.
• For instance, one recent UMD result: a silicon-nitride chip patterned with hundreds of microring resonators arranged in a 2-D grid that produced a nested topological frequency comb. Light circulated along the chip edge via topologically protected edge modes and produced a frequency comb structure—a direct application in photonic circuits using semiconductor fabrication. jqi.umd.edu+1

What this enables / applications

• Robust light transport: Because the edge modes are topologically protected, they can travel around sharp corners, through defects, or across disordered regions with minimal back-scattering or loss. This is highly desirable in integrated photonic circuits where fabrication imperfections are inevitable. Hafezi Group+1
• Frequency combs and spectroscopy: The nested topological frequency comb from UMD is a proof-of-concept device that uses topological photonics for generating multiple evenly‐spaced laser frequencies, useful in metrology, atomic clocks, sensing, or communications. jqi.umd.edu+1
• Quantum light and integrated photonics: The group is exploring the interface of topological photonic structures with quantum emitters (e.g., quantum dots) or nonlinear optics, which could yield new architectures for quantum information, photon routing, and photonic chips with built-in resilience. DRUM+1

Challenges and research directions

• Translating topological photonics from proof-of-concept physics to practical chip-scale devices involves addressing losses, fabrication tolerances, coupling to emitters or fibers, and integrating active components.
• Exploring nonlinear and quantum regimes of topological photonics: for example, how topological protection interacts with optical nonlinearities, photon‐photon interactions, or gain/loss (non‐Hermitian effects). jqi.umd.edu+1
• Extending these ideas in semiconductor‐compatible platforms (e.g., silicon photonics, III–V materials) with high integration, high volume manufacturability, and broad bandwidth operation.

At the University of Maryland (UMD), the research theme of Quantum Optoelectronics in Semiconductors bridges advanced materials science, device physics and quantum engineering, and focuses on integrating light-matter quantum phenomena into semiconductor platforms for next-generation optoelectronic and quantum technologies.

Key Features of the Research

• Quantum emitter integration: UMD researchers work with semiconductor nanostructures (such as quantum dots, 2D materials, and heterostructures) embedded in photonic and electronic circuits to generate, modulate and detect quantum states of light (single photons, entangled photons) in scalable chip-forms. For example, the Joint Quantum Institute at UMD includes a group devoting effort to “quantum confined emitters” and “low-energy opto-electronics”. Waks Group
• Semiconductor-based optoelectronic materials tailored for quantum control: UMD is part of the Center for Integration of Modern Optoelectronic Materials on Demand (IMOD), funded by the National Science Foundation, which explores new semiconductor materials and manufacturing processes to enable devices such as single-photon sources, strong photon-photon interaction platforms, and quantum photonic sensors. Maryland Today+1
• Device architectures and photonic circuits: The research includes development of semiconductor optoelectronic devices configured for quantum regime operation: ultra-low‐loss waveguides, photonic crystal resonators, modulators and detectors that operate at cryogenic or near-quantum‐limit conditions. The aim is to bring devices typically found in lab-scale quantum optics into integrated semiconductor platforms.
• Quantum nonlinear and many-body optical effects in semiconductors: Recent UMD work demonstrates giant optical nonlinearities in atomically-thin semiconductor heterostructures (e.g., engineered exciton-Fermi polaron systems) that show promise for quantum optoelectronic applications (including few-photon switching) in semiconductor materials. JQI
• Applications toward quantum sensing, communication and computation: The overarching goal is to embed quantum-optical functionality—such as quantum light generation, coherent control, and detection—into semiconductors, enabling scalable hardware for quantum networks, quantum communications, secure sensing and eventually quantum computing architectures.

Why It Matters

• Traditional optoelectronics uses semiconductors for LEDs, lasers, photodetectors and solar cells; by bringing quantum phenomena into those devices, UMD positions semiconductor platforms to go beyond classical performance limits (e.g., entering regimes of single-photon sensitivity, entanglement, quantum coherence).
• The ability to fabricate quantum-optical devices using semiconductor‐compatible processes holds the promise of scaling quantum technologies (which often remain in bespoke laboratory setups) into manufacturable systems.
• Semiconductor quantum optoelectronic devices offer prospects for integration with existing electronic and photonic infrastructures, lowering the barrier from quantum research to real-world deployment (e.g., in communications, sensing, computing).

Challenges and Research Directions

• Material and interface quality: Achieving long quantum coherence and low optical loss in semiconductor devices is demanding; the integration of quantum emitters into complex photonic circuits must contend with fabrication imperfections, material defects and scattering.
• Operating environment and compatibility: Many quantum‐optical effects require cryogenic temperatures or specialized environments—translating these into devices operating at higher temperatures or more practical conditions is a key research direction.
• Integration of active quantum control: Going beyond passive quantum optical components (emitters, detectors) to include modulators, switches and interfaces compatible with quantum states is a major challenge.
• Scalability and manufacturability: The aim to move from laboratory prototypes to large-scale chips demands work in materials, process flows, system packaging, and cross-disciplinary collaborations between physics, materials science and electrical engineering.

At the University of Maryland, silicon photonics research develops chip-scale photonic circuits and semiconductor devices that guide, modulate, detect and process light on CMOS-compatible platforms—bridging nanofabrication, materials engineering, and quantum and classical photonic system design to create scalable, low-loss, manufacturable optical components and systems. photonics.umd.edu+1

Materials & device platforms.
UMD groups work across silicon-on-insulator and silicon-nitride photonic platforms as well as hybrid/heterogeneous integrations that couple III–V or other compound semiconductor micro-emitters to silicon waveguides. This multi-material focus enables on-chip lasers, high-Q resonators, modulators, and detectors while leveraging foundry processes for scale. Recent efforts include hybrid integration strategies to bring bright single-photon emitters and active devices into industry-scale silicon photonic circuits. chembolab.umd.edu+1

Integrated photonic circuit design & fabrication.
Teams at UMD design and fabricate photonic circuits (ring resonators, photonic crystals, waveguide lattices, delay lines and filters) using nanoscale lithography and characterization suites—covering design, simulation, test, and packaging—so devices can be prototyped and translated toward foundry processes. These capabilities support both classical optical communications/microwave-photonic functions and experiments in nonlinear and quantum optics. Srinivasan Group+1

Quantum and nonlinear photonics integration.
A major thrust at UMD is bringing quantum functionality to silicon photonics: integrating quantum emitters, achieving strong light–matter coupling in on-chip cavities, and building photonic processors for quantum error-correction and photonic quantum information experiments. UMD labs pursue nonlinear integrated photonics (few-photon switching, frequency combs) and hybrid platforms that enable quantum light sources and routing on a silicon photonic backbone. Waks Group+1

Systems & applications.
Silicon photonics at UMD targets a broad application space: high-bandwidth optical interconnects and microwave-photonic signal processing, compact frequency combs and metrology, photonic sensors, and quantum communications/computing building blocks (photon sources, routing, and on-chip error-mitigation). The emphasis is on device performance and system-level integration so photonic chips can be coupled to fibers, electronics, and cryogenic quantum hardware. trend.umd.edu+1

Collaborations, facilities, and translation.
Research is highly interdisciplinary—linking ECE, Physics (JQI), materials science, and centers that support foundry-style fabrication and test—so UMD can move concepts from theory to nanofabricated prototypes and pursue partnerships with industry and national labs for scale-up and commercialization. me.umd.edu+1

Challenges & research directions.
Key technical challenges being addressed include reducing propagation loss and coupling losses, improving emitter indistinguishability and brightness when hybrid-integrated, operating in realistic (including cryogenic) environments, engineering nonlinearities for few-photon operation, and developing packaging/process flows that are compatible with silicon foundries. Ongoing work focuses on overcoming these limits to enable robust, manufacturable silicon photonic systems for both classical and quantum applications. PubMed+1

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The Joint Quantum Institute (JQI), founded in 2006, is the cornerstone of UMD’s quantum enterprise. Formed as a research partnership between UMD and NIST and supported by the Laboratory for Physical Sciences, JQI is dedicated to the broad study of quantum science—from theory to experiment—on a host of platforms.

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The Joint Center for Quantum Information and Computer Science (QuICS) is a collaboration with NIST that expands research at the junction of quantum physics, computer science and information theory, enabling the full potential of quantum computing.

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The Condensed Matter Theory Center (CMTC) has made pioneering contributions to exotic approaches to quantum computing now being pursued worldwide.

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The Quantum Materials Center (QMC) is a specialized research center in the Department of Physics where scientists synthesize and explore novel quantum materials with the goal of enabling new quantum device platforms utilizing superconductivity, topology and other quantum phenomena.

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The LPS Qubit Collaboratory (LQC) is a national Quantum Information Science Research Center hosted at the National Security Agency’s Laboratory for Physical Sciences (LPS) at UMD. LQC advanced the development of qubits through an innovative model of collaboration between the government and a wide range of partners across the country.

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Established through a partnership between IonQ, Inc., a leading developer of quantum computing devices, and the University of Maryland, the National Quantum Laboratory (QLab) enables the scientific community to pursue world-leading research through hands-on access to a commercial-grade quantum computer. UMD-affiliated students, faculty, researchers, staff and partners across the country have an unprecedented opportunity to gain experience with IonQ’s industry-leading trapped-ion quantum computer hardware and collaborate with IonQ scientists and engineers.

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Funded by the National Science Foundation (NSF) and led by the University of Maryland, the NSF Quantum Leap Challenge Institute for Robust Quantum Simulation brings together computer scientists, engineers and physicists from five academic institutions and the federal government. The institute is focused on developing quantum simulation devices that can understand, and thereby exploit, the rich behavior of complex quantum systems.

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